Highway snow and ice control typically is carried out by governmental authorities with the use of dump trucks which are seasonally modified by the addition of snow-ice treatment components. These components will include the forwardly-n-mounted plows and rearwardly-mounted mechanisms for broadcasting materials such as salt or salt-aggregate mixtures. The classic configuration for the latter broadcasting mechanisms included a feed auger extending along the back edge of the dump bed of the truck. This hydraulically driven auger effects a metered movement of material from the bed of the truck onto a rotating spreader disk or xe2x80x9cspinnerxe2x80x9d which functions to broadcast the salt across the pavement being treated. To maneuver the salt-based material into the auger, the dump bed of the truck is progressively elevated as the truck moves along the highway to be treated. Thus, when into a given run, the dump bed will be elevated, dangerously raising the center of gravity of the truck under inclement driving conditions.
An initial improvement in the controlled deposition of salt materials and the like has been achieved through the utilization of microprocessor driven controls over the hydraulics employed with the seasonally modified dump trucks. See Kime, et al. in U.S. Pat. No. Re 33,835, entitled xe2x80x9cHydraulic System for Use with Snow-Ice Removal Vehiclesxe2x80x9d, reissued Mar. 3, 1992. This Kime, et al. patent describes a microprocessor-driven hydraulic system for such trucks with a provision for digital hydraulic valving control which is responsive to the instantaneous speed of the truck. With the hydraulic system, improved controls over the extent of deposition of snow-ice materials is achieved. This patent is expressly incorporated herein by reference.
Investigations into techniques for controlling snow-ice pavement envelopment have recognized the importance of salt in the form of salt brine in breaking the bond between ice and the underlying pavement. Without a disruption of that bond, little improvement to highway traction will be achieved. For example, the plow merely will scrape off the snow and ice to the extent possible, only to leave a slippery coating which may be more dangerous to the motorist than the pre-plowed road condition.
When salt has been simply broadcast over an ice laden pavement from a typical spinner, it will have failed to form a brine of sufficient salt concentration to break the ice-pavement bond. The result usually is an ice coated pavement, in turn, coated with a highly dilute brine solution developed by too little salt, which will have melted an insufficient amount of ice for traction purposes. This condition is encountered often where granular salt material contains a substantial amount of xe2x80x9cfines xe2x80x9d. Fines are very small salt particles typically generated in the course of transporting, stacking, and storing road maintenance salt in dome-shaped warehouses and the like.
Road snow-ice control studies have revealed that the activity of ice melting serving to break the noted ice-pavement bond is one of creating a saltwater brine of adequate concentration. In general, an adequate salt concentration using conventional dispersion methods requires the distribution of unacceptable quantities of salt on the pavement. Some investigators have employed a saturated brine as the normal treatment modality by simply pouring it on the ice covered highway surface from a lateral nozzle-containing spray bar mounted behind a truck. A result has been that the- thus-deposited brine concentration essentially immediately dilutes to ineffectiveness at the ice surface, with a resultant dangerous liquid-coated ice highway condition.
Attempting to remove ice from pavement by dissolving the entire amount present over the entire expanse of pavement to be treated is considered not to be acceptable from an economical standpoint. For example, a one mile, 12 foot wide highway lane with a xc2xc inch thickness of ice over it should require approximately four tons of salt material to make a 10% brine solution and create bare pavement at 20xc2x0 F. Technical considerations for developing a salt brine effective to achieve adequate ice control are described, for example, by D. W. Kaufman in xe2x80x9cSodium Chloride: The Production and Properties of Salt and Brinexe2x80x9d, Monograph Series 145 (Amer. Chem. Soc. 1960).
The spreading of a combination of liquid salt brine and granular salt has been considered advantageous. In this regard, the granular salt may function to maintain a desired concentration of brine for attacking the ice-pavement bond and salt fines are more controlled by dissolution in the mix. The problem of excessive salt requirements remains, however, as well as difficulties in mixing a highly corrosive brine with particulate salt. Typically, nozzle injection of the brine is the procedure employed. However, attempts have been made to achieve the mix by resorting to the simple expedient of adding concentrated brine over the salt load in a dump bed. This approach is effective to an extent. However, as the brine passes through the granular salt material, it dissolves the granular salt such that the salt will not remain in solution and will recrystallize, causing bridging phenomena and the like inhibiting its movement into a distribution auger.
The problem of the technique of deposition of salt in a properly distributed manner upon the highway surface also has been the subject of investigation. Particularly where bare pavement initially is encountered, snow/ice materials utilized in conventional equipment will remain on the highway surface at the time of deposition only where the depositing vehicles are traveling at dangerously slow speeds, for example about 15 mph. Above those slow speeds, the material essentially is lost to the roadside. Observation of materials attempted to be deposited at higher speeds shows the granular material bouncing forwardly, upwardly, and being broadcast over the pavement sides such that deposition at higher speeds is ineffective as well as dangerous and potentially damaging to approaching vehicles. That latter damage sometimes is referred to as xe2x80x9ccollateral damagexe2x80x9d. However, the broadcasting trucks themselves constitute a serious hazard when traveling, for example at 15 mph, particularly on dry pavement, which simultaneously is accommodating vehicles traveling, for example at 65 mph. The danger so posed has beer, considered to preclude the highly desirable procedure of depositing the salt material on dry pavement just before the onslaught of snow/ice conditions. Of course, operating at such higher speeds with elevated dump truck beds also poses a hazardous situation.
In addition to the hazards posed by slow speeds of travel, trucks utilized for snow-ice treatment exhibit difficulties negotiating ice coated highways, particularly where uphill grades are encountered. One technique for driving upon such ice coated hills has been to turn the trucks around, activate the rear mounted salt broadcasting spinner and travel up the incline in reverse gear. This procedure achieves only marginal traction and is manifestly an undesirable solution to this traction problem.
Kime, et al., in U.S. Pat. No. 5,318,226 entitled xe2x80x9cDeposition of Snow-ice Treatment Material from a Vehicle with Controlled Scatterxe2x80x9d, issued Jun. 7, 1994, (incorporated herein by reference) describes an effective technique and mechanism for controlling the scatter of the so-called granules at higher speeds. With the method, the salt materials are propelled from the treatment vehicle at a velocity commensurate with that of the vehicle itself and in a direction opposite that of the vehicle. The result is an effective suspension of the projected materials over the surface under a condition of substantially zero velocity with respect to or relative to the surface of deposition. Depending upon vehicle speeds desired, material deposition may be provided in controlled widths ranging from narrow to wider bands to achieve a control over material placement. Another xe2x80x9czero-velocityxe2x80x9d method for salt distribution employing a different apparatus approach has been introduced by Tyler Industries, Inc. of Benson, Minn. See xe2x80x9cRoads and Bridgesxe2x80x9d, Dec. 1995, Scranton Gillette Communications, Inc., Des Plaines, Ill. See also, U.S. Pat. No. 5,842,649 and 5,947,391 by Beck et al.
A practical technique for generating a brine of sufficient concentration to break the ice pavement bond is described in U.S. Pat. No. 5,988,535 entitled xe2x80x9cMethod and Apparatus for Depositing Snow-Ice Treatment Material on Pavement by Kime, issued Nov. 23, 1999 and incorporated herein by reference. With this technique, ejectors are employed to deposit a salt-brine mixture upon a highway as a relatively narrow, continuous and compact band of material. To achieve such narrow band material deposition at practical highway speeds of 40 mph or more, the salt-brine mixture is propelled from the treatment vehicle at a velocity commensurate with that of the vehicle itself and in a direction opposite that of the vehicle. Further, the material is downwardly directed at an acute angle with respect to the plane defined by the pavement. When the salt-brine narrow band is deposited at the superelevated side of a highway lane, the resultant concentrated brine from the band is observed to gravitationally migrate toward the opposite or downhill side of the treated lane to provide expanded ice clearance. The result is a highly effective snow-ice treatment procedure with an efficient utilization of salt materials. Because the lanes of modem highways are superelevated in both a right and a left sense, two spaced apart salt ejectors are employed to deposit the narrow band concentration at positions corresponding with the tire tracks of vehicles located at the higher or elevated portion of a pavement lane. A feature of the apparatus of this system is its capability for being mounted and demounted upon the dump bed of a conventional highway maintenance truck in a relatively short interval of time. As a consequence, these damp trucks are readily available for carrying out tasks not involving snow-ice control. Additionally, the apparatus is configured such that the dump beds remain in a lowered or down position throughout their use, thus improving the safety aspect of their employment during inclement winter weather.
The present invention is addressed to apparatus and method for depositing salt based snow-ice treatment material upon pavement from a vehicle moving at practical highway speeds. A truck having a dump bed is employed for this deposition which is customized to deposit mixed salt and brine material on a highway as a continuous narrow band which is configured to evoke and maintain a brine at the highway having a salt concentration effective to break an ice-pavement bond. Two of these continuous bands may be deposited from a forward location on the truck such that the bands are formed within the path of travel of its rear wheels. As these wheels encounter the deposited salt band, they function to compact or compress the continuous granular salt pile into the ice formation on the pavement to enhance the development of a high salt concentration brine and to promote resultant breakup of the ice layer. In addition to this highly desirable aspect, the snow-ice control truck is afforded substantially improved traction over pavement ice so as to enjoy a capability for negotiating highway grades with greater control and safety.
Even though the truck is customized to carry salt and brine materials and the apparatus of their deposition, its dump bed advantageously may be used for other tasks not concerned with snow-ice control. In this regard, the bottom surface of the dump bed is flat and surmounts an elongate, centrally disposed chamber housing a salt transport mechanism which is positioned below the dump bed surface. Fortuitously, salt granules carried in the dump bed can be caused to dynamically migrate toward the central transport mechanism with the simple expedient of slightly elevating the dump bed and then dropping it in a xe2x80x9cdown fastxe2x80x9d operator controlled maneuver. The flat surface dump bed readily is converted for other tasks by covering over the centrally disposed chamber with a sequence of cover plates.
The ejectors which are mounted forwardly on the vehicle are utilized to form the narrow bands function to eject the salt based material rearwardly toward the rear tire assemblies both at a velocity commensurate with the forward speed of the vehicle and at a downward direction toward the pavement. The extent of this downward direction is that of an acute angle of about 15xc2x0 with respect to the instantaneous plane of the highway pavement. This downward direction causes the narrow band deposition to occur within a relatively short distance from the ejector mechanism such that the continuous band shaped piles of granular salt and brine are formed with stability upon the highway pavement just prior to being traveled over and compacted by the rearwardly disposed wheel assemblies of the truck.
Maneuvering of granular salt to the forwardly mounted, spaced apart ejector mechanisms initially is by operation of the centrally located bed mounted transport mechanism. When the bed is in its lower or down position, this transport assembly passes granular salt to a cross transport mechanism mounted upon the truck frame just forwardly of the front of the dump bed. This transversely oriented transport mechanism both supports the two ejector mechanisms and conveys the granular salt to their inputs. To provide an operational feature wherein the operator of the vehicle may optionally deposit a salt band from one or both ejectors, the bed transport mechanism is configured as two independently driven augers. These independent augers feed granular salt to two directionally configured flight sequences of an auger utilized as the cross transport mechanism. Thus, an operator election for depositing salt from one or both ejector mechanisms is made by driving one or both of the bed supported augers.
A brine formation and dispensing assembly is mounted forwardly on the truck just behind its cab and positioned over the cross transport assembly. This brine developing mechanism dispenses formed brine liquid into the cross transport mechanism for carrying out an efficient mixing of it with granular salt. The assembly is charged through an upwardly opening hopper defining structure, a portion of which extends over the top of the cab. With the arrangement, this brine formation structure can be loaded with brine forming granular materials utilizing the same front end loader vehicle as is used for filling the dump bed with salt material. An additional advantage accrues from this vehicle mounted brine formation and dispensing assembly. Motorists in the northern climates are familiar with highway signage advising that the decks of bridges ice over before earth-supported normal roadways. The in situ brine formation assembly can be used to dispense brine from a spray bar extending transversely across the truck as the trucks encounter bridge deck pavement prior to the formation of ice. Because the brine is placed upon the bridge deck before the onslaught of icing weather, it becomes quite effective in combating the initial formation of ice on the bridge.
Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter. The invention, accordingly, comprises the apparatus and the method possessing the construction, combination of elements, arrangement of parts, and steps which are exemplified in the following description.
For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in connection with the accompanying drawings.